DUT continuity test with only digital IO structures apparatus and methods associated thereof

Abstract

A method and system for determining short, open, and good connections using digital input and output (IO) structures in a device under test (DUT) continuity test, through the combined methods of using resistance-capacitance (RC) delay, time domain reflectometry (TDR), and forcing voltage on to a single IO pin of the DUT while measuring voltage on remaining IO pins of said DUT. In one embodiment, the combined methods are executed without the DUT in a test socket to produce a first set of test values and also with the DUT in a test socket to produce a second set of test values. The first and second sets of test values are compared to determine if one or more circuits of the DUT have a short circuit, an open circuit, or are a good (have an electrical connection that is not a short circuit or an open circuit) circuit.

The invention claimed is: 
     
       1. A method for identifying open circuits using time domain reflectometry (TDR) comprising:
 providing a test setup comprising a tester coupled to a DUT board; 
 placing all tester pins on said tester in a high impedance state; 
 configuring a first tester I/O pin connected to a first DUT I/O pin as a tester output driving logic high; 
 configuring said first tester I/O pin as a tester output logic low to introduce a negative edge signal; 
 configuring said first tester I/O pin in a high impedance state; 
 configuring said first tester I/O pin as tester input sampling a highest reliable sample rate generating a sample count; 
 recording said sample count in a non-transitory computer storage readable medium; 
 continually sampling said first tester I/O pin during prior two configuring and recording steps at highest reliable sample rate for enough time for reflection to propagate from said tester to said DUT and back to said tester; 
 wherein said sampling step is based on detecting an increased voltage after time zero and generates sample values; 
 storing said sample values into said non-transitory computer storage readable medium; 
 repeating said configuring, sampling, and storing steps until all tester I/O pins connected to DUT I/O pins have been characterized and said sample values stored in said non-transitory computer storage readable medium; 
 repeating said configuring, sampling, storing and prior repeating steps a desired number of times to determine a range of sample for each tester I/O and DUT I/O pin pair which represents an open circuit between said tester I/O and DUT I/O pin pair; 
 inserting a DUT into said test setup; 
 repeating said configuring, sampling and storing steps generating a recorded value for each tester I/O and DUT I/O pin pair; 
 comparing said recorded value with said sample values to determine if the insertion of said DUT has changed a recorded pattern for each tester I/O and DUT I/O pin pair. 
 
     
     
       2. The method of  claim 1 :
 wherein said comparing step indicating that the presence of said DUT has changed said recorded pattern for each tester I/O and DUT I/O pin pair and said recorded pattern includes more ‘1’ values recorded, then an open circuit in the continuity data of said DUT is detected. 
 
     
     
       3. The method of  claim 1 :
 wherein said comparing step indicating that the presence of said DUT has changed said recorded pattern for each tester I/O and DUT I/O pin pair and said recorded pattern includes less ‘1’ values recorded, then either a short or good connection is detected in the continuity data of said DUT. 
 
     
     
       4. The method of  claim 1 :
 wherein said comparing step indicating that the presence of said DUT has not changed said recorded pattern for each tester I/O and DUT I/O pin pair and said recorded pattern includes ‘1’ values, then an open circuit in DUT continuity is likely. 
 
     
     
       5. The method of  claim 1 :
 wherein said comparing step indicating that the presence of said DUT has not changed said recorded pattern for each tester I/O and DUT I/O pin pair and said recorded pattern does not include ‘1’ values, then either a short or good connection is likely.